I really enjoy building and riding ultra light road bikes. I'm planning on building a super light MTB but will I be wasting my money and ending up with something that has more disadvantages than advantages?

I weigh 65kg and will be riding pretty up and down quite fast and technical Surrey trails.

I'm sure this subject has come up before but I couldn't find it in the search function. Some advise on this would be appreciated.

I can't even imagine a fully suspension bike 2kg lighter, and the shortcuts you took to get it there. That's moderately frightening.

Personally, my general motto is the bike has to go up fast, and down faster. A light bike that breaks, bends, or flats all the time does me no good. If you ride down the hills like Sabine Spitz, sure, that may work for you.

I don't subscribe to the fact a bike can be too light (well barring trying to actually get on one in a hurricane!), making sure you have the right parts to be strong 'enough' at that weight is what is key! Your quite clear about what you want to use the bike for which helps a lot.

Of course it won't be cheap, each kilo below 10kg will about double the cost of the bike, mine is 10.1Kg (to 10.2 depending on the tyres fitted) and costs me as it stands less than £600 (nearly all parts bought used), but to go much lighter will cost a lot more.

I am confident you can put together a 6.5kg hardtail MTB (not full suspension LeDuke) that is sufficiently durable for my needs. The question is more would the advantages of more efficient climbing be outweighed by things like poor handling and low traction.

My 5kg Storck road bike just feels superb, does a 6.5kg MTB?

krzysiekmz I'll post a full build list in due course. I'm looking at a few options. The only bits I'm sure of so far is Open frame, German A Kilo fork and the usual Ax Lightness/ Schmolke stuff. Wheel wise I'm contemplating a Tune rim and hub combination weighing around 1.2kg.

I have a ~6.8kg rigid single speed (Morati fork, Giant XTC frame) and it is a blast to ride and flies up hills.

But when the going gets rough, it literally bounces all over the trails. Frame and fork are both very forgiving, but with so little mass under you when you are flying through roots and rocks it really is a job to keep it pointed straight.

That being said, the bike is >8yrs old, is loads of fun, and I'm not getting rid of it anytime soon. It is one of many bikes in our house, and doesn't get ridden too often, which certainly helps the longevity. But I would ride it more, if my wife hadn't commandeered it since it is so much fun.

I say go for it as long as it won't be the only trail bike you ride. It'll be a blast to combine with some other rising as well, and certainly you'll find some trails where you won't ever want to ride anything else.

A light bike wont only help you on the climbs. One of the reasons singletrack is so much harder/tiring then fireroads is you are constantly flicking the bike around that corner, hopping it over that log. Yanking it to the side a bit to go in-between those two rocks there. Having 2 less kg's to flick around is definitely something you notice at the end of a big ride.

Thanks for the comments and encouragement. It will be my only MTB as the road will continue to be my main past time. I will probably only get off road once a week. I won't be racing but I want to learn how to go hard and fast. I'm a bit of a fitness and ability freak. I'm looking forward to being the best I can at this very tough and technical sport.

It would be great to hear more from those who have light bikes and why they like them or in fact dislike them.

Nino Schurter rides what is probably one of the lightest bikes in the WC. He can get away with it because he's a wizard when things get rough.

His bike, by all accounts, is 7.8kg. World Cup courses have grown increasingly technical; there is a reason you see guys moving to larger wheels and slightly heavier bikes. The days of 15lb bikes on 1.8" tires are more or less over. Sure, there are a few, here and there, that still ride 560mm bars and bar ends, but for the most part, people are going with "heavier" bikes, wider bars, bigger tires. Those bikes are still under 20lbs, but not nearly as light as they used to be.

Same with local XC races. Now, I'm not sure where you ride. If your area is double track and easy, smooth singletrack, a super light bike with Maxxlites or Furious Freds may work for you. Where I live, and where I grew up riding (NY, and OR) you need some tread on the tires, some actual air volume, and wider bars to really haul ass. Plenty of people can produce a lot of power, and scream uphill. But races are increasingly won on the downhill and technical sections. Is that 500g you saved on tires going to help you, or hinder you? In most cases, particularly if you're all go and no show (road racer on an MTB), it will put you on your ass and out of contention.

I say this because I learned this the hard way. Once upon a time, in my early 20s, I was a Cat 1 road guy who started racing MTBs. I chopped my handlebars down and made everything as light as possible. I wasn't Geoff Kabush; I couldn't pull off Maxxlites. I didn't have the technical ability to do that. I'd blow people away on the climbs and lose that time on the descents. I went for a ride with a former Olympian MTB racer from OR, and he gave me some advice, on both bike set up and bike handling. I took it to heart, and applied to both my bike and my riding. A year later, I upgraded to Pro on the dirt.

6.5kg is not too light when it's reliable and doesn't feel iffy. For next year I'd like to build a 650B or 29er hardtail around that weight.

A few years ago I spec'd a custom Tomac Carbide SL fully at 6.8kg for a trade show. The wheels were 876 grams built around Tune's Dezibel rear hub and Innolite rims. Other than having full ceramic bearings in the rear hub, it was perfectly rideable.

_________________“I always find it amazing that a material can actually sell a product when it’s really the engineering that creates and dictates how well that material will behave or perform.” — Chuck Teixeira

I think skyfire1202 is still a member here. His bike 12.32lbs / 5.58kg

Sure, some people wouldn't think Maxlites etc are daily riders but skyfire1202 still races his bikes. It's not like it would be heavy with with a SID, Crest wheelset, Racing Ralphs and Ashima rotors anyway.

I'd like to see more full-size ultralight bikes. Ones that normal weight riders could ride the crap out of. Something that's perfectly rideable and doesn't have any weight limits or dubious componentry. I've built and contributed to a number of extremely light builds, though most of them I wouldn't ride myself.

_________________“I always find it amazing that a material can actually sell a product when it’s really the engineering that creates and dictates how well that material will behave or perform.” — Chuck Teixeira

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